Heat can be an important issue in a variety of mechanical transducer applications, including electrical applications and others, are related to pressure sensors, resonator structures and other frequency-reference devices. For example, in semiconductor applications, circuits often generate a significant amount of heat due to a variety of operational conditions, physical conditions (e.g., close proximity, lack of cooling) and other conditions. Such heat can introduce a variety of undesirable operational conditions, introducing performance and reliability issues. In addition, variation in temperature, whether via heating or cooling, can affect the operating temperature of devices and, accordingly, the performance thereof.
One type of electrical application subject to such temperature-related conditions involves resonators. For instance, the mechanical resonant frequency of devices constructed from Silicon varies with temperature. Accordingly, resonators implementing Silicon have experienced temperature-related changes in resonant frequency.
In many resonator applications, a variety of approaches have been implemented for addressing, controlling or otherwise compensating for temperature. Generally, temperature compensation methods for resonators have been classified as active or passive. Many active compensation techniques use power in order to reduce the temperature coefficient of frequency (TCF) into the desirable range. For instance, voltage has been applied to alter the resonant frequency of a resonator. Passive compensation approaches have used non-powered approaches to tune the resonant frequency of resonator materials, such as those involving the introduction of different materials to a particular type of resonator.
While previous approaches to addressing heat (and temperature) related issues have been implemented, controlling or otherwise compensating for temperature changes in resonators continues to be challenging. For example, approaches involving the introduction of materials with mismatched CTE's may introduce stress induced hysteresis, processing difficulties due to large thermal stresses, restrictions on material selection for clean processes and CMOS compatibility, and undesirable sensitivity to package stress.
These and other characteristics have been challenging to the implementation and manufacture of resonators.